1. Overview & Packing Types
Packed columns use random dumped packing or structured packing to provide interfacial area for gas-liquid mass transfer in distillation, absorption, and stripping operations. Packing offers advantages over trays including lower pressure drop, higher capacity, and better efficiency — critical for vacuum distillation, large columns, and low liquid rates.
Random packing
Pall rings, Raschig rings, saddles
Lower cost, easy to install; HETP = 2-5 ft; good for smaller columns (< 4 ft diameter).
Structured packing
Mellapak, Flexipac, Montz Pak
Higher efficiency (HETP 1.5-3 ft), lower ΔP, higher capacity; best for large columns.
Applications
Distillation, amine treating, glycol dehydration
Packed columns ideal for low liquid rates, foaming systems, corrosive service.
Advantages vs trays
Lower ΔP, higher turndown, better for vacuum
Packing ΔP ~50% lower than trays; turndown ratio 4:1 vs 2:1 for trays.
Random Packing Types
| Packing Type | Size Range | HETP (ft) | Typical Use |
|---|---|---|---|
| Raschig rings (ceramic/metal) | 0.5-3 inch | 3-6 | Legacy design; rarely used in new construction |
| Pall rings (metal/plastic) | 1-3.5 inch | 2-4 | Improved over Raschig; common in amine contactors |
| Intalox saddles (ceramic) | 1-3 inch | 2.5-5 | Lower pressure drop than rings; gas treating |
| IMTP (metal) | 1-3.5 inch | 1.8-3 | High performance random; distillation, absorption |
| Flexirings (metal/plastic) | 1-3 inch | 2-3.5 | Modern random packing; good capacity and efficiency |
IMAGE: Random vs Structured Packing Comparison
Side-by-side photos showing: (L) Pall rings, IMTP, Raschig rings dumped packing; (R) Structured packing corrugated sheets with Y-pattern
Structured Packing Types
| Packing Type | Surface Area (ft²/ft³) | HETP (ft) | Void Fraction (%) |
|---|---|---|---|
| Mellapak 250Y (Sulzer) | 82 | 1.5-2.0 | 95% |
| Mellapak 350Y | 115 | 1.3-1.8 | 93% |
| Mellapak 500Y | 164 | 1.0-1.5 | 90% |
| Flexipac 2Y (Koch-Glitsch) | 85 | 1.5-2.0 | 95% |
| Montz B1-250 (Julius Montz) | 82 | 1.5-2.2 | 96% |
| High capacity packing (large dia.) | 50-70 | 2.5-3.5 | 97-98% |
Packing Materials Selection
- Metal (304/316 SS, carbon steel, titanium): Most common for distillation and gas treating; good heat transfer; avoid carbon steel in corrosive service or high moisture.
- Plastic (polypropylene, PVDF): Corrosive service (HCl, H₂SO₄), water treating; temperature limited to < 200-250°F; lower cost than metal.
- Ceramic: Very corrosive/high temperature service (> 400°F); brittle (handle with care); higher cost; used in sulfuric acid plants, HF alkylation.
- FRP (fiberglass-reinforced plastic): Large columns with corrosive service; temperature limited < 250°F; good for amine contactors, water treatment.
When to use packing vs trays: Packing is preferred for: (1) Vacuum service (low ΔP critical), (2) Corrosive systems (ceramic/plastic packing available), (3) Foaming systems (no liquid holdup on trays), (4) Low liquid rates (< 5 gpm/ft² causes poor tray distribution), (5) Large columns (> 10 ft diameter; structured packing more economical than large trays). Trays are preferred for: (1) Solids handling (packing plugs easily), (2) Wide operating range (trays better turndown than random packing), (3) Fouling service (trays easier to clean), (4) Very low surface tension (liquid channeling in packing).
2. HETP & Mass Transfer Efficiency
Height Equivalent to a Theoretical Plate (HETP) measures packing efficiency. Lower HETP means better mass transfer performance and shorter column height for a given separation. HETP depends on packing type, system properties, and operating conditions (flow rates, pressure).
HETP Definition
HETP Concept:
HETP = Height of packing that provides separation equivalent to one theoretical stage (equilibrium stage)
Required packing height:
H = N_theoretical × HETP
Where:
H = Total packing height (ft)
N_theoretical = Number of theoretical stages (from Fenske, McCabe-Thiele, or process simulation)
HETP = Height equivalent to theoretical plate (ft)
Example:
Distillation requires 20 theoretical stages
Structured packing: HETP = 2.0 ft
Required height = 20 × 2.0 = 40 ft of packing
Compare to tray column:
Tray efficiency = 75%
Actual trays = 20 / 0.75 = 27 trays
Tray spacing = 24 inches
Height = 27 × 2 ft = 54 ft (plus 15 ft for top/bottom spaces = 69 ft total)
Packing column: 40 ft packing + 15 ft = 55 ft total (shorter column)
Factors Affecting HETP
- Packing type and size: Structured packing has lower HETP (1.5-3 ft) than random packing (2-5 ft). Within random packing, smaller size → lower HETP but higher ΔP. 1-inch packing HETP ~50% lower than 2-inch packing.
- Liquid rate: HETP decreases with increasing liquid rate up to loading point, then increases as approach flooding. Optimum liquid rate typically 60-80% of flood.
- Gas rate: Higher gas rate reduces HETP (better mass transfer) until approaching flood. At flood, HETP increases dramatically due to liquid entrainment.
- Physical properties: Low viscosity, high diffusivity → lower HETP. Surface tension affects wetting; poor wetting → higher HETP. Density difference (ρ_L - ρ_V) affects flooding and capacity.
- System difficulty: Easy separations (high relative volatility α) achieve lower HETP. Difficult separations (α close to 1.0) have higher HETP due to approach to equilibrium limitations.
Bravo-Fair-Rocha HETP Correlation
HETP for Structured Packing (Bravo et al., 1985):
HETP = H_OG + H_OL
Where:
H_OG = Height of transfer unit, gas phase
H_OL = Height of transfer unit, liquid phase
H_OG = (u_G / k_G × a_e) × (1 / (1 + λ))
H_OL = (L / k_L × a_e) × (λ / (1 + λ))
Where:
u_G = Superficial gas velocity (ft/s)
L = Liquid mass flux (lb/hr·ft²)
k_G = Gas-phase mass transfer coefficient
k_L = Liquid-phase mass transfer coefficient
a_e = Effective interfacial area (ft²/ft³)
λ = Stripping factor = (m × G / L)
m = Slope of equilibrium line
Mass transfer coefficients from vendor correlations or empirical data.
Typical HETP values for Mellapak 250Y at atmospheric distillation:
- Easy separation (α = 2.5): HETP = 1.5 ft
- Moderate separation (α = 1.5): HETP = 2.0 ft
- Difficult separation (α = 1.2): HETP = 2.8 ft
Onda HETP Correlation (Random Packing)
Onda et al. (1968) for Random Packing:
Effective interfacial area:
a_e / a = 1 - exp[-1.45 × (σ_c / σ)^0.75 × Re_L^0.1 × Fr_L^-0.05 × We_L^0.2]
Where:
a_e = Effective wetted area (ft²/ft³)
a = Total packing surface area (ft²/ft³)
σ = Surface tension (dyne/cm)
σ_c = Critical surface tension of packing material (33 for ceramic, 61 for steel)
Re_L = Liquid Reynolds number = L / (a × μ_L)
Fr_L = Froude number = L² × a / (ρ_L² × g)
We_L = Weber number = L² / (ρ_L × σ × a)
Gas-phase mass transfer:
k_G × a = C_G × (D_G / d_p) × Sc_G^-0.5 × Re_G^0.7
Liquid-phase mass transfer:
k_L × a = C_L × (D_L / d_p) × Sc_L^-0.5 × Re_L^(1/3)
Where:
D_G, D_L = Diffusivities (gas, liquid)
d_p = Packing nominal size
Sc = Schmidt number
Re_G, Re_L = Reynolds numbers (gas, liquid)
C_G, C_L = Empirical constants (depend on packing type)
This rigorous approach used in process simulators (Aspen, ProMax, HYSYS).
Vendor HETP Data
Packing vendors provide HETP data from distillation tests (typically chlorobenzene/ethylbenzene system):
| Packing | Test System | Pressure (psia) | HETP (ft) | Capacity (ft/s) |
|---|---|---|---|---|
| Mellapak 250Y | C6/C7 | 14.7 | 1.6 | 3.2 |
| Mellapak 350Y | C6/C7 | 14.7 | 1.4 | 2.8 |
| Flexipac 2Y | C6/C7 | 14.7 | 1.7 | 3.0 |
| 2-inch Pall rings (metal) | C6/C7 | 14.7 | 2.8 | 2.2 |
| 1.5-inch IMTP | C6/C7 | 14.7 | 2.2 | 2.5 |
HETP scale-up: Vendor HETP data from small test columns (1-3 ft diameter) must be adjusted for commercial-scale columns (> 4 ft diameter). Scale-up factors account for liquid maldistribution and wall effects. For structured packing in columns > 6 ft diameter, multiply test HETP by 1.1-1.2. For random packing, multiply by 1.2-1.5 depending on column diameter and distributor quality. Poor liquid distribution can increase HETP by 50-100%, making distributor design critical.
3. Pressure Drop & Flooding Limits
Pressure drop through packing increases with gas and liquid flow rates. At high flow rates, liquid accumulates in the packing (loading) and eventually floods, causing catastrophic loss of separation. Design must stay below flooding velocity with adequate margin (70-85% of flood).
IMAGE: Generalized Pressure Drop Correlation (GPDC) Chart
Log-log plot with Flow Parameter (Y-axis) vs Capacity Parameter (X-axis), constant ΔP lines (0.1, 0.25, 0.5, 1.0 in H₂O/ft), flood line
Generalized Pressure Drop Correlation (GPDC)
Strigle (1987) / Leva Correlation:
Y-axis (flow parameter):
Y = (L/G) × √(ρ_G / ρ_L)
Where:
L = Liquid mass flow rate (lb/hr)
G = Gas mass flow rate (lb/hr)
ρ_L = Liquid density (lb/ft³)
ρ_G = Gas density (lb/ft³)
X-axis (capacity parameter):
X = (G² × F_p × μ_L^0.1) / (ρ_G × (ρ_L - ρ_G) × g_c)
Where:
F_p = Packing factor (ft⁻¹) - vendor-provided constant
μ_L = Liquid viscosity (cP)
g_c = Gravitational constant (32.17 lb·ft/lbf·s²)
Pressure drop (ΔP/H) read from GPDC chart for given X and Y at constant ΔP/H lines (0.1, 0.2, 0.5, 1.0 in H₂O/ft packing).
Flooding occurs at ΔP/H → ∞ (vertical line on chart).
Packing factors (F_p):
- 1-inch Pall rings (metal): 56 ft⁻¹
- 2-inch Pall rings (metal): 31 ft⁻¹
- Mellapak 250Y: 28 ft⁻¹
- Mellapak 350Y: 42 ft⁻¹
- 1.5-inch IMTP: 36 ft⁻¹
Flooding Velocity Calculation
Flooding Correlation (Kister-Gill, 1991):
Flooding occurs when:
u_flood = C_flood × √[(ρ_L - ρ_G) / ρ_G]
Where:
u_flood = Superficial gas velocity at flooding (ft/s)
C_flood = Flooding constant (function of packing, L/G ratio)
C_flood from vendor data or generalized correlation:
C_flood = 0.8 to 3.5 ft/s (depending on packing type and liquid rate)
Higher C_flood → higher capacity packing
Typical values:
- Structured packing (Mellapak 250Y): C_flood = 2.5-3.2 ft/s
- Random packing (2-inch Pall rings): C_flood = 1.8-2.2 ft/s
- High-capacity structured: C_flood = 3.0-3.8 ft/s
Design gas velocity:
u_design = 0.70 to 0.85 × u_flood
Example:
ρ_L = 50 lb/ft³ (hydrocarbon liquid)
ρ_G = 0.3 lb/ft³ (hydrocarbon vapor)
Packing: Mellapak 250Y, C_flood = 2.8 ft/s
u_flood = 2.8 × √[(50 - 0.3) / 0.3]
u_flood = 2.8 × √166 = 2.8 × 12.9 = 36 ft/s
Design velocity (80% of flood):
u_design = 0.80 × 36 = 28.8 ft/s
Column diameter:
A = Q_gas / u_design
D = √(4A / π)
If Q_gas = 100,000 ft³/hr = 27.8 ft³/s:
A = 27.8 / 28.8 = 0.965 ft²
D = √(4 × 0.965 / π) = 1.11 ft → Use 1.5 ft ID column (standard size)
Pressure Drop Example Calculation
Example: Amine Contactor Pressure Drop
System:
Gas flow = 10 MMscfd = 1.157 ft³/s at operating conditions
Liquid (amine) flow = 50 gpm = 0.111 ft³/s
ρ_G = 0.8 lb/ft³
ρ_L = 62 lb/ft³
μ_L = 2.5 cP
Column diameter = 4 ft (area = 12.57 ft²)
Packing: 2-inch Pall rings, F_p = 31 ft⁻¹
Gas velocity:
u_G = 1.157 / 12.57 = 0.092 ft/s
Mass flow rates:
G = 1.157 ft³/s × 0.8 lb/ft³ = 0.926 lb/s = 3,334 lb/hr
L = 0.111 ft³/s × 62 lb/ft³ = 6.88 lb/s = 24,768 lb/hr
Flow parameter:
Y = (24,768 / 3,334) × √(0.8 / 62) = 7.43 × 0.114 = 0.85
Capacity parameter:
X = (3,334² × 31 × 2.5^0.1) / (0.8 × (62-0.8) × 32.17)
X = (11,115,556 × 31 × 1.096) / (0.8 × 61.2 × 32.17)
X = 377,900,000 / 1,575 = 239,937
From GPDC chart at X = 240,000, Y = 0.85:
ΔP/H ≈ 0.3 in H₂O/ft packing
For 20 ft of packing:
ΔP_total = 0.3 × 20 = 6 in H₂O = 0.22 psi
This is acceptable for typical amine service.
Operating Regimes
| Operating Point | % of Flood | Pressure Drop | HETP | Comment |
|---|---|---|---|---|
| Pre-loading | < 50% | Very low (linear with flow) | Slightly high | Inefficient use of packing; large column required |
| Loading region | 50-80% | Moderate (starts to increase) | Optimum (lowest) | Typical design range; good efficiency and margin |
| Near flood | 80-95% | High (rapidly increasing) | Increasing | Risky; little margin for upsets or fouling |
| Flooding | > 100% | Extreme (liquid backs up) | Infinite (no separation) | Column inoperable; liquid carryover to overhead |
Turndown and fouling margin: Design at 70-80% of flood provides adequate margin for: (1) Turndown capability (can reduce throughput without losing efficiency), (2) Fouling (solids, polymers, or corrosion products reduce effective area), (3) Off-spec operation (higher-than-design reflux ratios or liquid rates), (4) Future capacity increases (can operate up to 90-95% flood in clean service with careful monitoring). Columns designed at > 85% flood are prone to operational problems and flooding during upsets.
4. Liquid & Gas Distribution Design
Proper liquid distribution is the single most important factor for packing performance. Maldistribution increases HETP by 50-200% and causes channeling, reduced capacity, and premature flooding. High-quality distributors are essential, especially for large-diameter columns and structured packing.
Liquid Distribution Requirements
Distributor Quality Metrics:
Irrigation density:
ρ_irrigation = L / A_column
Where:
L = Liquid flow rate (gpm)
A_column = Column cross-sectional area (ft²)
Minimum irrigation for good wetting:
Random packing: 5 gpm/ft²
Structured packing: 2-3 gpm/ft² (more wettable surface)
Below minimum → poor wetting → dry spots → high HETP
Drip point density (pour points per ft²):
For random packing: 3-5 points/ft²
For structured packing: 8-12 points/ft² (critical due to low spreading)
Distributor uniformity:
Std deviation of liquid delivery to each drip point < 10% of mean
Poor distribution (std dev > 20%) → 50-100% increase in HETP
IMAGE: Liquid Distributor Types
Diagram showing cross-sections of: orifice pan, perforated pipe (trough), tunnel cap tray, and spray nozzle distributors with drip points labeled
Distributor Types
| Distributor Type | Drip Points/ft² | Turndown | Application |
|---|---|---|---|
| Spray nozzle | N/A (continuous spray) | 2:1 | Quench zones, top distributors in cooling/washing |
| Orifice pan (gravity flow) | 3-5 | 2:1 | Random packing, small columns (< 6 ft diameter) |
| Perforated pipe (ladder trough) | 5-8 | 2.5:1 | Random and structured packing, moderate size columns |
| Tunnel cap tray | 8-12 | 3:1 | Structured packing, large columns, critical separations |
| Liquid arm/spray | 10-15 | 3:1 | Premium distributor for structured packing > 8 ft diameter |
IMAGE: Packed Column Internals Cutaway
Cross-section showing: top distributor, packing beds, collectors/redistributors, support plates, hold-down grids, gas inlet horn, liquid sump
Redistributor Spacing
Maximum Packing Height Without Redistribution:
For random packing:
H_max = 2 × D_column or 20 ft, whichever is less
For structured packing:
H_max = 1.5 × D_column or 30 ft, whichever is less
Beyond this height, liquid maldistribution accumulates and reduces efficiency.
Redistributors are required to collect liquid and re-distribute uniformly.
Example:
8 ft diameter column with structured packing
Maximum bed height = 1.5 × 8 = 12 ft
If total packing height = 50 ft:
Use 4 beds of 12.5 ft each, with 3 redistributors
Distributor stack-up:
- Initial distributor (top)
- 12.5 ft packing (Bed 1)
- Collector + Redistributor 1
- 12.5 ft packing (Bed 2)
- Collector + Redistributor 2
- 12.5 ft packing (Bed 3)
- Collector + Redistributor 3
- 12.5 ft packing (Bed 4)
- Bottom (liquid outlet)
Each redistributor adds ~2-3 ft to column height.
Gas Distribution (Bottom Inlet)
Gas inlet design prevents liquid entrainment and ensures uniform vapor distribution:
- Gas inlet nozzle velocity: Limit to 50-75% of erosional velocity to prevent liquid entrainment from bottom liquid pool. V_nozzle < 100 ft/s typical for hydrocarbon service.
- Inlet gas distribution: Use gas horn or gas distributor to spread vapor uniformly across column cross-section. Poor gas distribution causes preferential flow paths and reduces HETP by 20-50%.
- Gas inlet momentum: Limit momentum to prevent "jet effect" that disrupts liquid flow in packing. Use larger nozzle or diffuser if gas momentum is high.
- Inlet gas separation: If feed is two-phase, use inlet chimney tray or demister to separate liquid before entering packing. Liquid slugs cause flooding and damage to packing.
Feed Entry Design
Feed Nozzle Sizing (Two-Phase Feed):
For feed entering mid-column:
Nozzle velocity (two-phase):
u_nozzle = Q_gas / A_nozzle
Limit to avoid entrainment:
u_nozzle < 0.5 × u_erosional
Where:
u_erosional = C / √ρ_mix
C = 100-150 for non-corrosive service
ρ_mix = Two-phase density
Feed distribution:
Use feed box or distributor pipe to spread feed across column cross-section.
Poor feed distribution → liquid/vapor jet impinges on packing → mechanical damage and maldistribution.
Best practice:
Design feed distributor with same quality as liquid distributors (8-12 drip points/ft²).
For high-velocity feeds, use vapor-liquid disengagement space below feed point.
Distributor cost vs performance: High-quality distributors cost $50K-$200K for large columns but are essential for achieving design HETP. A cheap distributor saves $100K but increases HETP by 50%, requiring 50% more packing height to achieve separation. For a 10 ft diameter × 50 ft tall column, adding 25 ft of packing costs $300K-$500K in additional column shell and packing — far more than the distributor savings. Always invest in high-quality distributors (8-12 points/ft² for structured packing, 5-8 points/ft² for random packing) to achieve design performance.
5. Packing Selection Guide
Packing selection balances performance (HETP, capacity), cost (packing material, installation), and operability (fouling, corrosion). Structured packing offers best performance but at higher cost; random packing is more economical for smaller columns and less critical separations.
Decision Matrix: Random vs Structured
| Factor | Random Packing | Structured Packing | Recommendation |
|---|---|---|---|
| Column diameter | Best for < 6 ft | Best for > 6 ft | Use random for small, structured for large columns |
| Efficiency requirement | HETP 2-5 ft | HETP 1.5-3 ft | Use structured for difficult separations (high stages) |
| Pressure drop | 0.2-0.5 in H₂O/ft | 0.1-0.2 in H₂O/ft | Use structured for vacuum or low-ΔP service |
| Capital cost | $20-50/ft³ | $100-200/ft³ | Random packing ~50-70% cheaper |
| Turndown ratio | 2-3:1 | 4-5:1 | Structured better for varying loads |
| Fouling susceptibility | Lower (larger voids) | Higher (can plug) | Use random for fouling service |
| Installation | Dump in place (easy) | Hand-stacked (labor-intensive) | Random simpler to install in field |
Application-Specific Recommendations
- Amine treating (CO₂/H₂S removal): Use 2-inch Pall rings or IMTP random packing. Liquid rate typically low (20-40 gpm/ft²), random packing adequate. Fouling from degradation products requires periodic packing removal/cleaning (random packing easier).
- Glycol dehydration contactors: Use 1-2 inch random packing (Pall rings, saddles). Low liquid rate (5-15 gpm/ft²), corrosion potential (use stainless or plastic packing). HETP not critical (2-4 theoretical stages typical).
- Distillation (hydrocarbons): Use structured packing (Mellapak, Flexipac) for columns > 6 ft diameter. High efficiency needed (20-50 stages common). Vacuum columns always use structured packing (low ΔP).
- Fractionation (NGL, BTX, aromatics): Use high-efficiency structured packing (Mellapak 350Y, 500Y). Difficult separations (α < 1.5) require HETP < 2 ft. Large-diameter columns (10-20 ft) benefit from structured packing capacity.
- Stripping (sour water, air stripping): Use random packing or low-cost structured. HETP not critical (5-10 stages typical). Fouling potential (use large packing size, 2-3 inch).
Packing Size Selection (Random Packing)
| Column Diameter (ft) | Recommended Packing Size | Minimum D/d_p Ratio |
|---|---|---|
| < 2 | 0.5-1 inch | 8:1 |
| 2-4 | 1-1.5 inch | 10:1 |
| 4-8 | 1.5-2 inch | 12:1 |
| 8-12 | 2-3 inch | 15:1 |
| > 12 | 3-3.5 inch (or use structured) | 20:1 |
Economic Analysis Example
Random vs Structured Packing Cost Comparison:
Column: 6 ft ID × 40 ft packing height
Service: Hydrocarbon distillation, 25 theoretical stages
Option 1: Random packing (2-inch Pall rings, metal)
HETP = 3.0 ft
Required height = 25 × 3.0 = 75 ft
Packing volume = π × 3² × 75 = 2,121 ft³
Packing cost = 2,121 ft³ × $40/ft³ = $84,840
Installed cost (packing + distributor + install) = $150,000
Option 2: Structured packing (Mellapak 250Y)
HETP = 2.0 ft
Required height = 25 × 2.0 = 50 ft
Packing volume = π × 3² × 50 = 1,414 ft³
Packing cost = 1,414 ft³ × $150/ft³ = $212,100
Distributor (high quality required) = $75,000
Installed cost = $350,000
Additional column height for random packing:
ΔH = 75 - 50 = 25 ft extra
Column shell cost = 25 ft × π × 6 ft × $200/ft² = $94,200
Total cost:
Random: $150,000 + $94,200 = $244,200
Structured: $350,000
Structured packing is $105,800 more expensive (43% premium).
However, structured packing advantages:
- Lower pressure drop (50% less energy for overhead condenser compression if vacuum)
- Higher turndown ratio (better for varying loads)
- Lower HETP uncertainty (better distributor quality)
Decision: For critical separation or vacuum service, structured packing justified.
For atmospheric pressure, non-critical service, random packing more economical.
Hybrid packing approach: Many modern columns use hybrid packing: structured packing in critical sections (top and bottom where high purity required) and random packing in middle sections (where separation is easier). Example: Depropanizer with 60 stages total could use 15 stages structured packing (top), 30 stages random packing (middle), 15 stages structured packing (bottom). This reduces total packing cost by 30-40% while maintaining product purity specifications. Consult process licensor or packing vendor for optimized hybrid configuration.
Common Packing Problems and Solutions
| Problem | Symptom | Root Cause | Solution |
|---|---|---|---|
| Flooding | High ΔP, liquid carryover to overhead | Operating above flood point; fouling; distributor plugging | Reduce throughput; clean packing; inspect distributor |
| Channeling | Poor separation; low ΔP; uneven liquid distribution | Maldistribution; packing settling; wall channeling | Inspect/replace distributor; add redistributors; install wall wipers |
| High HETP | More stages required than design; off-spec product | Fouling; poor distribution; operating at low load | Clean packing; improve distributor; increase reflux to load packing |
| Corrosion | Metal packing degradation; pressure drop increase | Acidic/basic service with carbon steel packing | Replace with stainless steel, plastic, or ceramic packing |
| Packing breakage | Ceramic packing cracked; metal packing deformed | Hydraulic shock; liquid slugs; improper installation | Replace packing; install surge protection; inspect feed system |
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